/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2004 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" and
 *    "Apache Lucene" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
 *    written permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    "Apache Lucene", nor may "Apache" appear in their name, without
 *    prior written permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 * $Id: StringFilter.java,v 1.2 2004/05/29 20:24:50 chedong Exp $
 */

package org.apache.lucene.search;

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.TermDocs;
import org.apache.lucene.index.TermEnum;

import java.io.IOException;

import java.util.BitSet;


/**
 * A Filter that restricts search results to a exactly match a string or start
 * with prefix
 *
 * @author Che, Dong
 */
public final class StringFilter extends Filter {
    //~ Instance fields --------------------------------------------------------

    /** DOCUMENT ME! */
    private String field = null; //compare field

    /** DOCUMENT ME! */
    private String s = null; //compare string

    /** DOCUMENT ME! */
    private boolean strict = true; //true: strict mach,false: prefix match 

    //~ Constructors -----------------------------------------------------------

    /**
     * Constructs a filter for field <code>f</code> matching <code>
     * compare</code> String
     *
     * @param f DOCUMENT ME!
     * @param compare DOCUMENT ME!
     */
    public StringFilter(String f, String compare) {
        field = f;
        s = compare;
    }

    /**
     * Creates a new StringFilter object.
     *
     * @param f DOCUMENT ME!
     * @param compare DOCUMENT ME!
     * @param str DOCUMENT ME!
     */
    public StringFilter(String f, String compare, boolean str) {
        field = f;
        s = compare;
        strict = str;
    }

    //~ Methods ----------------------------------------------------------------

    /**
     * Constructs a filter for field <code>f</code> matching string start with
     * <code>prefix</code>.
     *
     * @param field DOCUMENT ME!
     * @param prefix DOCUMENT ME!
     *
     * @return DOCUMENT ME!
     */
    public static StringFilter isLike(String field, String prefix) {
        StringFilter result = new StringFilter(field, prefix, false);

        return result;
    }

    /**
     * Returns a BitSet with true for documents which should be permitted in
     * search results, and false for those that should not.
     *
     * @param reader DOCUMENT ME!
     *
     * @return DOCUMENT ME!
     *
     * @throws IOException DOCUMENT ME!
     */
    public final BitSet bits(IndexReader reader) throws IOException {
        BitSet bits = new BitSet(reader.maxDoc());
        TermEnum terms = reader.terms();

        try {
            //exactly match
            if (strict == true) {
                Term stop = new Term(field, s);

                while (terms.next()) {
                    if (terms.term().compareTo(stop) == 0) {
                        TermDocs termDocs = reader.termDocs(terms.term());

                        try {
                            while (termDocs.next()) {
                                bits.set(termDocs.doc());
                            }
                        } finally {
                            termDocs.close();
                        }
                    }
                }
            } else { //prefix match

                while (terms.next()) {
                    if (terms.term().field().equals(field)
                            && terms.term().text().startsWith(s)
                       ) {
                        TermDocs termDocs = reader.termDocs(terms.term());

                        try {
                            while (termDocs.next()) {
                                bits.set(termDocs.doc());
                            }
                        } finally {
                            termDocs.close();
                        }
                    }
                }
            }
        } finally {
            terms.close();
        }

        return bits;
    }

    /**
     * DOCUMENT ME!
     *
     * @return DOCUMENT ME!
     */
    public final String toString() {
        StringBuffer buffer = new StringBuffer();
        buffer.append(field);
        buffer.append(":");

        if (strict == true) {
            buffer.append("is " + s);
        } else {
            buffer.append("is prefix match " + s);
        }

        return buffer.toString();
    }
}
